Bukkit

@mze9412

Did some tests last evening with adding teleport in onVehicleUpdate:

• Tried teleport player but, it does not like it. Player get stuck and cart stop moving if you try to teleport a player attached to the cart entity.
• Tried teleport cart. Somehow helped a bit with higher speeds. I could get carts moving 10x (1000%), but it does not solve the occasional missing move events that visually eject player and get it to fall in the void, even at 100% normal Notch speed with CraftBukkit server on localhost (garanteed no network packet loss and high flow rate).
• Thgough I did not try casting an event here as it would have caused a cascade of recursive events. (There may be a better place to do this).
• My fears are, unless ejecting player, copying cart, destroying original and re attaching player to the new copy of the cart (as in the full world teleport), the client will also miss some and it will cause unwanted visual glitches and server load.

It look like the missing move events or chunk data is a problem upstream, either in the MM event handlers or in CraftBukkit or worse, a design flaw in minecraftserver client protocol. Earlier CB 1.2.5 did not expose this issue with falling into the void or visually eject move lag then fastforward.

Here's what I did in MinecartManiaCoreListener onVehicleUpdate event handler line 56:

if (minecart.isMoving()) {
    if (minecart.getDirectionOfMotion() != minecart.getPreviousDirectionOfMotion()) {
      MinecartManiaCore.callEvent(new MinecartDirectionChangeEvent(minecart, minecart.getPreviousDirectionOfMotion(), minecart.getDirectionOfMotion()));
minecart.setPreviousDirectionOfMotion(minecart.getDirectionOfMotion());
    }
// test crap workaround client lag in move events
    Entity passenger = minecart.getPassenger();
    if (passenger != null) {
//        passenger.teleport(minecart.getLocation()); // Teleport player does not work
        minecart.teleport(minecart.getLocation()); // Teleport cart may help in higher speeds
    }
}

Ok for documentation.

I found a small bug. With sign and chest [deposit items] and [all items], OAK SAPLING (item 6 data 7) never go to cart.

@mze9412

Pretty funny, but informative IRC chat sniplet about handling client-side out of sync move events:

[[irc://irc.esper.net/bukkitdev|IRC esper.net #bukkitdev]]

<leagris> Hello. I am looking for a documented or proper method to detect out of sync (due to network or server lag) clients. Use cas is, client receive late or missing move events, so I'd cast a teleport event to get it back in sync.
<ammar2> leagris: there really is no "proper" way of doing that without modifications to the client
<leagris> Typically, player attached to a moving minecart entity. Minecart move too fahr away (faster than client can sync). At some time, client is too much out of sync to handle the moves. But it can get in sync again if it receive a teleport event.
<leagris> I'd like to avoid casting  systematic periodic teleport event (just in case) and only cast it where the client is identified as out of sync.
<leagris> ammar2, do you mean the actual client version does not scream some event when it get out of sync with the server?
<ammar2> leagris: yes
 leagris: in case you haven't figured already, the networking side of minecraft is pretty terrible.
<leagris> thanks ammar2, I totally agree :)

@mze9412

I guess the fix may not be as tough as you look like to think of.

The MinecartManiaMinecart.teleport method could be used here.

Instead of only testing a world change, it could test location change against int org.bukkit.Server.getViewDistance ( ) so to cast a minecart teleport event when the move exceed the configured view distance in server.properties.

I'd need to dig further in the code to find out when to invoke teleport (either scheduled or tested during each move.

MinecartManiaMinecart.java#L240

	public MinecartManiaMinecart teleport(Location location) {
		if (!location.getWorld().equals(getWorld())) {

@mze9412

Falling into the void

Server or network lag case

Chunks are not provided fast enough to the client:

• At client side, the cart visually stops moving
• Server side, the cart pursue it's ride.

Client receive late playermove events in the next 5-10 seconds:

• Client fast forward to the new position

Client get out of sync because missing or out of bounds late playermove events:

• Client visually eject player, removes display of cart entity.
• After like 15s or if client attempt playermove, out of sync client tries to get surrounding chunk data but the server sends chunk data for the real known server side player location. So the client has no chunk data to display and handle around the visual location as known client side. Player fall into the void without taking dammage.
• As the cart terminates it's server-side ride (eject, cart destroyed or returned item), the client resync to the new location.

Possible workarround

Likely, while playermove events are stacking, an out of sync client will not accept much out of time or out of bound distance late moves and will not update client side player location. But it will accept a playerlocation update event as sent when eject, cart destroy…

A possible workarround would be to force periodically sending playerlocation/teleport events to the client instead of just playermove events.

Really need a new wiki, this plugin is unusable (for me and i think for all new user). Hard to find explanations.